What I was talking about was using my old 5 gallon as the hlt. Heat 3 or 4 gallons to strike temp, the refill it and while its mashing heat 3 or 4 gallons to sparge temp. Then I can drain the mash wort out straight to my new boil kettle then sparge with what was in my old kettle that has been heating during the mash time.

I am thinking of doing the same - converting my 8G BK to an electric HLT .. but I think I will wait to get 2 15G pots so I can do 10G batches..